The invention relates to aqueous film-forming binder dispersions or emulsions which are used as rapid-hardening coatings and may contain plasticizers, flatting agents, fillers, pigments, additives and assistants.
Aqueous emulsions of unsaturated polyester resins are known from European Patent Specification No. 3,337, corresponding to U.S. Pat. No. 4,281,068. They contain two unsaturated polyesters having .beta.,.gamma.-ethylenically unsaturated ether groups, and one of these polyesters additionally contains cocondensed polyalkylene glycol radicals. These known emulsions are free of monomers and contain waxes or paraffins as barrier agents to prevent inhibition of polymerization by atmospheric oxygen. These known emulsions can be hardened, in mixture with photoinitiators, with the aid of UV radiation or can be polymerized, in mixture with peroxides, at room temperature. They are proposed for the open-pore coating of wood or wood-like materials.
These known polyester emulsions have the disadvantage that they require a relatively long drying time, and, when using higher temperatures, an intermediate drying step over an evaporation zone is necessary to remove the water, since otherwise the film is made milky by water inclusions. When using a continuous operation where very short hardening times are important, the hardening time is not adequate to ensure that the material can be stacked or wound up.